Fractal Characteristics of Free Surface Profiles of Metal Sheets under Equi-Biaxial Tension

Free surface profiles of aluminum sheets under equi-biaxial tension are examined by employing three kinds of fractal analyses, i.e., the zeroset, power spectrum and box-counting metods.With an increase in plastic strain, long-wavelength components of the surface profiles become dominant, and their fractal structure tends to become constant beyond a certain strain.It is found that both surface roughness and fractal dimensions depend on the equivalent strain, independent of the stress ratio.A method for simulating the surface roughening behavior is presented by utilizing the power spectrum method